Riot Games released a new video detailing their plans for the near future which included a shop overhaul and major updates to the item system with mythic items taking the spotlight.
League of Legends Season 11 will bring along a new tier of items - mythics. These items will be more powerful than the currently highest tier which is legendary. Examples of legendaries are complete items like Infinity Edge or Rabadon's Deathcap.
While the mythics will have quite a few stat bonuses themselves, they will not be superior to legendaries in that way. Instead, they will augment a playstyle and grant additional bonuses to legendaries in a player's inventory. To keep things in check, everyone will be able to have only one mythic.
Riot showed several examples of mythic items in the video below but let's focus on Crimson Shieldbow for the moment, in order to properly demonstrate how this new tier will work.
Raw stats from the Shieldbow will grant players 50 attack damage, 15 per cent attack speed, 20 per cent critical chance and 12 per cent lifesteal. It also acts as an anti-burst item as it procs a shield in a manner similar to Maw of Malmortius and grants an additional 20 per cent lifesteal for eight seconds. The bonuses are beefy, but even if they are more powerful than a regular legendary, the difference is fairly small.
What sets this item apart is the Mythic Passive which adds eight armour and magic resistance for each legendary item in a character's inventory. This way, the AD carries might finally be able to protect themselves from assassins but that remains to be seen when all the new items get revealed.
Oh and there is a mythic that makes everyone deal true damage like Vayne would.